Before OSI it was TCP/IP Model. OSI (Open Systems Interconnection) Model was just a reference/logical model. OSI model was the first model published in 1984 by the International Organization for Standardization (ISO). It was designed to show the transmission of data between different layers.
TCP/IP was designed and developed by the Department of Defense (DoD) in the 1960s and is based on standard protocols. TCP/IP stands for Transmission Control Protocol/Internet Protocol. In the OSI layer, there were 7 layers but in TCP/IP, there are 4 layers.
TCP/IP has 4-layer architecture, with each layer having specific functionality to perform. All these layers work to transmit the data from one person to another across the globe.
The application layer is used by the Network applications like google chrome, Edge browser etc... and these application protocols help to do web surfing. It is like a GUI Part. With the help of browsers you can access the necessary internet services.
Protocols: HTTP, FTP, SMTP, Telnet, POP, DNS, RCP
The Application layer contains two important layers Presentation Layer and Session Layer
This layer is responsible for encryption and decryption. It compresses the size of data for faster data connection. Data could be lossy or lossless. It is helpful in real-time video and audio conferencing.
This layer is responsible for opening the terminal and connecting two different computers. It performs two functions Authentication and Authorization. It also helps in reconnecting the broken signals.
Transport layer has 3 main roles to do, Segmentation, Flow control and Error Control
Data received from the session layer is divided into small frames and each segment contains source, destination, and the sequence number that help to resemble all the packets in order.
It controls the amount of data being transmitted. Example: There is one server and smartphone and the server transmits data with 100mbps while the smartphone can send and receive data up to 10mbps. So in this case the server reduces the bandwidth size to maintain consistency.
If some data doesn’t arrive at the destination then it sends a request to the server. Each packet contains checksums that help to find correct data.
Network layer has two main job to do Logical Addressing and Path destination.
In this network, the layer provides an IP address to each packet (segment) of data that helps to reach data from source to destination.
Select the best possible route to send and receive data.
It helps in mapping and casting. In this layer, bits are encoded and decoded in the frame.
It deals with error and flows control.
MAC: It deals with how to share links in the Point to Point or Broadcast process.